The present invention relates to effervescent dipeptide sweetener tablets for use primarily as a table-top sweetener in beverage systems such as coffee and tea which tablets contain a calcium carbonate-containing, stable carbonation system, citric acid, and a soluble pre-fixed form of APM present at least partly as the sweetener. The effervescent APM tablet has a rate of solubility which is significantly better than APM alone or when compressed in a non-effervescent tablet. In addition, utilization of the quick-dissolving, stable form of APM (60% APM/40% Mor-Rex) with a dry carbonation system having excellent stability properties (50% CaCO.sub.3 /50% Mor-Rex) produces an APM tablet which is not only rapidly soluble in aqueous-based systems, but is stable on storage and undergoes no degradation and loss of sweetness when stored at room temperature for extended periods of time. Still further, the calcium carbonate has been found to be uniquely suited as a repressor of the characteristic lingering sweet aftertaste of APM.
The dipeptide sweetener now commonly known as APM and identified specifically as the methyl ester of L-aspartyl-L-phenylalanine is estimated to have 150 to 200 times the sweetness of sucrose on a weight to weight basis. Among the limitations of this dipeptide sweetener are slow rate of dissolution, limited stability in aqueous systems, and a lingering sweet aftertaste. The modes of decomposition of APM are not too fully understood, but it does appear that the reactions that stem from the presence of APM in moisture lead to an unfavorable interaction with other materials such as aldehydes and ketones and also lead to undesirable decomposition products resulting in, at times, significant loss in sweetness.
Several attempts at increasing the solubility of APM have involved improving its flowability by combining the dipeptide with other powderous materials such as citric acid. However, the flowability of APM in granular mixtures with citric acid and other beverage mix ingredients is poor in that it tends to bridge the remaining ingredients such that the mix will now flow readily or discharge through high-speed packaging equipment. Even when the dipeptide per se is ground, or it is co-ground with other materials serving as dispersants, the ultimate mix produced leaves much to be desired in terms of the flowability thereof by reason of the aforesaid properties of the dipeptide itself; the composition tends to pack or bridge and have a high angle of repose.
The solubility of APM was recently disclosed in U.S. Pat. No. 3,761,288 issued Sept. 25, 1973 and herein incorporated by reference as being significantly improved by co-drying the same with an edible bulking agent, specifically dextrin, having a dextrose equivalent (D.E.) of about 4 to 20, preferably 5 to 10. Although the advantages of the resultant composition having the flowability and appearance of sucrose are apparent, there are obvious hygroscopicity problems that may be encountered if the dextrin material does not have a sufficiently high molecular weight.
Although formation of an APM tablet would be thought to have improved solubility due to the increase in density and consequent "sinking" affect in beverages, (APM tends otherwise to "float" on the surface of beverages) compressed APM tablets have extremely poor solubility in cold water and in some instances, even in hot aqueous-based systems.
Netherlands Pat. No. 7,207,426 issued to Hoffman-LaRoche and Company, on June 1, 1972, teaches the preparation of an effervescent tablet containing from 0.1 to 10 weight % of L-aspartyl-L-3-phenylalanine methyl ester, pharmacodynamically active substances and sodium bicarbonate, the bicarbonate acting as the sole effervescent agent to produce a non-foaming sweet pharmaceutal tablet. However, while sodium bicarbonate is an effective carbonation agent, on storage it tends to react with various substances such as anhydrous citric acid which is desirably present in some liquid beverage systems. Consequently, the tablet of this reference is limited to dry pharmaceutical preparations.